Figure 6.

Colorimetric detection of synthetic cathinones using a SCA2.1-based Cy7-displacement assay. (A) Signal gain measured via a plate reader from the Cy7-displacement assay with 12 synthetic cathinones (gray, with the three selection targets shaded) and 11 interferents (white) at a concentration of 50 μM with 3 μM SCA2.1 and 2 μM Cy7. Cross-reactivity is defined as the ratio of signal gain between the reference target ethylone and another synthetic cathinone or interferent multiplied by 100%. Error bars show standard deviations from three measurements. (B) Naked-eye detection of synthetic cathinones using a mixture of 5 μM SCA2.1 and 3.5 μM Cy7. The color of the solution changes to bright blue within seconds upon addition of 50 μM synthetic cathinones (a-l). However, the color appears as a faint blue color in the absence of target (-) or 50 μM of a wide range of interferents (m-w).